Fluid enhanced ablation therapy involves the introduction of a fluid into a volume of tissue to deliver a therapeutic dose of energy in order to destroy tissue. The fluid can act as a therapeutic agent delivering thermal energy into the tissue volume—thermal energy supplied from the fluid itself (e.g., a heated fluid) or from an ablation element that provides thermal energy using, e.g., radio frequency (RF) electrical energy, microwave or light wave electromagnetic energy, ultrasonic vibrational energy, etc. This therapy can be applied to a variety of procedures, including the destruction of tumors.
One example of fluid enhanced ablation therapy is the SERF™ ablation technique (Saline Enhanced Radio Frequency™ ablation) described in U.S. Pat. No. 6,328,735, which is hereby incorporated by reference in its entirety. Using the SERF ablation technique, saline is passed through a needle and heated, and the heated fluid is delivered into a target volume of tissue surrounding the needle. In addition, RF electrical current is simultaneously passed through the tissue between an emitter electrode positioned on the needle and a remotely located return electrode. The saline acts as a therapeutic agent to deliver its thermal energy to the target volume of tissue via convection, and the RF electrical energy can act to supplement and/or replenish the thermal energy of the fluid that is lost as it moves through the tissue. The delivery of thermal energy via the movement of fluid through tissue can allow a greater volume of tissue to be treated with a therapeutic dose of ablative energy than is possible with other known techniques. The therapy is usually completed once the target volume of tissue reaches a desired therapeutic temperature, or otherwise receives a therapeutic dose of energy.
A common challenge in fluid enhanced ablation therapy is determining the extent of the target volume of tissue that has received a therapeutic dose of thermal energy. Known techniques for monitoring therapy progress include measuring the temperature of various portions of the target volume of tissue directly. Exemplary devices and methods for conducting such monitoring are described in U.S. Pat. Pub. No. 2012/0277737, which is hereby incorporated by reference in its entirety.
However, measuring the temperature of various portions of the target volume of tissue is not necessarily an effective technique for monitoring therapy progress. This is because it is often impractical to include more than a few temperature sensors on a single device, and the sensors can only report the temperature of the target volume of tissue in their immediate location. As a result, it can be difficult to monitor the overall shape of the treated volume of tissue.
Still further, misplacement of the needle or other fluid introduction device, or adjacent anatomical features that have high blood flow (e.g., capillaries, veins, etc.) can result in undesired and unexpected fluid flow. This unexpected fluid flow can direct therapeutic energy in an unexpected manner, thereby altering the shape and size of the treated volume of tissue that has received a therapeutic dose of thermal energy. Techniques for remotely monitoring the temperature of the target volume of tissue can report that the temperature is not rising as expected, but may not show where the heated fluid is flowing to and what the altered treated volume of tissue looks like.
Accordingly, there is a need in the art for improved systems and methods for monitoring fluid enhanced ablation therapy.